The move is expected within the next few months. The 68-year-old Ratner will remain chairman.

Ratner is making the move, sources close to the executive said, to lighten his load after a decade spent fighting off heavy opposition to his Atlantic Yards project before finally opening up the 18,000-seat Barclays Center last September.

Gilmartin, 48, joined Forest City in 1994 as an assistant vice president for commercial development. She worked her way up the ranks, becoming executive vice president in 2007.

“This is less about Bruce leaving and more about it being MaryAnne’s time,” said one source, who added the change won’t affect the Barclays Center or the Nets.